In most foundry casting operations, a pattern is introduced into a box-like structure called a mold flask and moist sand is formed under pressure around the pattern. The pattern is then removed from the sand and hot metal is poured into the cavity where it sets or solidifies. The sand used consists basically of fine sand with a number of additives such as clay, binders, and Sea-Coal, which are mixed with water to produce a mechanical mixture which can be formed under pressure and retain its shape. In most foundry operations, the amount of moisture in the sand prior to the pouring of the hot metal will vary from 3% to 7 or 8%, depending upon the type of metal being poured.
In the usual foundry operation, after the metal solidifies in the cavity in the sand mold, the castings are generally passed over a machine called a shakeout, usually of vibratory nature, where the sand is shaken loose from the casting. During the metal pouring operation, of course, heat is transferred from the metal to the sand. Some of this heat is dissipated by evaporation of some of the moisture in the sand, but a good deal of the heat is retained by the sand. In modern foundries, the sand is reused, mold after mold, and the total sand used would continue to increase in temperature to an unusable point. Therefore, it has been the practice to provide a method of cooling the sand before it is reused in subsequent molds. To form a good mold, the temperature of the sand ideally should be under 125.degree. F. The average temperature of the sand when the casting is removed from the mold can range from 200.degree. F. to 600.degree. F., or more, depending upon the cooling time and the sand-to-metal ratio in the mold.
There are several methods used for cooling sand such as, for example, leaving it in a pile overnight or for some period of time, and allowing the heat to be lost naturally. This method requires a great deal of space, a great deal of sand, together with rather heavy material handling apparatus. In other cases, the sand is passed through a fluid bed cooler in which ambient air is passed through the bed while it is being conveyed to cause evaporation of the moisture and cooling of the sand. Fluid bed coolers are expensive, and variations in the ambient temperature and humidity drastically affect the cooling rate. Furthermore, fluid bed coolers require the use of large dust collectors in order to prevent air pollution, etc.
Additionally, means must be provided, either as part of the shakeout or fluid bed cooler, for breaking up any clumps or lumps of sand which adhere together by reason of the entrained binders. This further complicates the system.